In mass production of soft contact lenses, specifically soft contact lenses which are worn only once and which are disposed of after use, a large number of soft contact lenses must be manufactured in a relatively short period of time. This may be performed with the aid of reusable molds comprising male and female mold halves in a closed-loop production process. Typically, a lens forming material is introduced into one of the male and female mold halves, the mold halve are then assembled to form the mold, and the lens forming material between the molding surfaces of the male and female mold halves is then polymerized and/or cross-linked, to form the lens. After demolding of the lens, the reusable molds are cleaned and dried and are then reused for production of the next lens. Suitable lens forming materials include, but are not limited to, polymers and prepolymers based on polyvinyl alcohols (PVA) or silicone hydrogels (SiHy).
In order to meet the needs of the large number consumers large numbers of contact lenses having different lens parameters must be produced. Such lens parameters include, for example, refractive power, base curve radius, axes of toric lenses, etc. Thus, in order to be able to carry out all incoming orders within a short time large numbers of different types of contact lenses must be produced and held on stock, the different types of contact lenses being distinct from each other in at least one lens parameter. Depending on the incoming orders, lenses of one particular type must be produced in larger numbers than others in order to refill the stock so as to be in a position to carry out all incoming orders within a short time.
In the closed-loop production process, a certain number of contact lenses which may or may not be of different types are produced in one run through the loop, that is to say until the male and female mold halves are re-used again in a further run through the loop. Accordingly, a corresponding number of pairs of male and female mold halves are used in the production line. Each such pair of male and female mold halves used in the production line is called a “lot”, so that the number of lots corresponds to the number of pairs of male and female mold halves actually used in the production line. All contact lenses produced in the various loops of the production process with the same pair of male and female molds halves belong to the same lot.
For each contact lens produced, a clear allocation of the contact lens produced to the respective lot is vital for various reasons, and also a mix-up of lots must be avoided. By way of example, in case a problem is reported by a customer with respect to a particular contact lens (a contact lens having a particular set of lens parameters) it is helpful if the corresponding lot can be identified (that pair of male and female mold halves which has been used for the production of the particular contact lens that has caused the problem). Only identifying the lens parameters of the contact lens that has caused the problem is not sufficient, since it is possible that contact lenses having the same lens parameters have been produced on the production line even in the same loop but with different pairs of male and female mold halves. Thus, it is vital that each contact lens can be clearly allocated to the respective lot and also to avoid lot mix-up. In case each contact lens can be allocated to the respective lot, it is possible to check whether the mold halves that have been used for production of the particular contact lens that has caused the problem are in optimum condition. This is even more important in case a problem reoccurs within the same lot.
For a clear allocation of a contact lens to a respective lot and in order to avoid lot mix-up, it is already known to apply the lot number to the contact lens in a peripheral portion of the contact lens outside the central optical portion so that application of the lot number is not experienced by the person wearing the contact lens.
It is an object of the invention to provide an improved ophthalmic lens, in particular a contact lens such as a soft contact lens, which comprises additional information applied to the lens. It is a further object of the invention to provide an improved process of manufacturing such ophthalmic lenses in an automated production line.